MEXICO CITY (Reuters) - Mexico has made clear it will never pay for President Donald Trump's planned southern border wall, the country's economy minister said on Thursday, after the U.S. leader again insisted he would make Mexico pay for the barrier.

"The President of Mexico (Enrique Pena Nieto) has been very clear: Mexico will never pay for this wall," Economy Minister Ildefonso Guajardo wrote on Twitter after a day of meetings in Washington.

Trump told the Wall Street Journal in an interview published on Thursday that Mexico could pay for the wall, which he hopes will stem illegal immigration, "indirectly" through changes to the North American Free Trade Agreement (NAFTA).

Trump has said he will withdraw from NAFTA if the accord cannot be renegotiated in favor of the United States.